In vehicles of today it is common to use an exhaust driven turbocharger for compressing air to an inlet manifold of an internal combustion engine (hereinafter simply referred to as engine). The up-speeding of the turbocharger is dependent on the exhaust flow, which in turn is dependent on engine speed and engine torque. Hence, turbocharger response is a well-known problem with turbocharger engines at low engine speeds. The response problem becomes even more imminent with the new technologies to reduce CO2 where turbochargers are used to down-speed and/or downsize engines due to the fact that more energy to build up the higher boost pressure is needed. The response problem is a limiting factor in the pursue for CO2 reduction, also because of that in order to provide an acceptable drivability of a vehicle a certain power margin to handle instant power demands without the need of shifting gear is required. Such instant power demand may be due to e.g., increased road inclination or driver requested acceleration.
It is known to use various compressors, such as e.g., mechanical compressors or electric compressors, connected to the inlet manifold in order to improve the turbocharger response by feeding air to the inlet side before the turbocharger has speeded up. Using of mechanical compressors adds complexity, adds cost, may impair the durability, has negative impact on the NVH (Noise, Vibrations, Harshness) properties and may be difficult to control. Using of an electric compressor also has major drawbacks e.g., due to complexity, cost and the fact that the electric compressor needs to be provided with electrical power.
EP 2749751 A1 discloses an improved turbocharger system wherein a tank, recharged by use of e.g., a compressor for compressing a gas such as air into the tank, is used to push compressed gas into an exhaust manifold conduit or an exhaust manifold during a predetermined pulse duration time period in order to obtain initial turbocharger compressor spin-up. However, in order for the improved turbocharger disclosed in EP 2749751 A1 to utilize its full potential further improvements and optimizations are needed.
Thus, there is still a need and room for further improvements.